Alloying technique for fe-based bulk amorphous alloy

ABSTRACT

One embodiment provides a method of making an alloy feedstock, comprising: forming a first composition by combining Fe with a first nonmetal element; forming a second composition by combining Fe with a plurality of transition metal elements; forming a third composition by combining the second composition with a second nonmetal element; and combining the first composition with the third composition to form an alloy feedstock.

All publications, patents, and patent applications cited in this Specification are hereby incorporated by reference in their entirety.

BACKGROUND

A large portion of the metallic alloys in use today are processed by solidification casting, at least initially. The metallic alloy is melted and cast into a metal or ceramic mold, in which it solidifies. The mold is stripped away, and the cast metallic piece is ready for use or further processing. The as-cast structure of most materials produced during solidification and cooling depends upon the cooling rate. There is no general rule for the nature of the variation, but for the most part the structure changes only gradually with changes in cooling rate. On the other hand, for the bulk-solidifying amorphous alloys the change between the amorphous state produced by relatively rapid cooling and the crystalline state produced by relatively slower cooling is one of kind rather than degree—the two states have distinct properties.

Bulk-solidifying amorphous alloys, or bulk metallic glasses (“BMG”), are a recently developed class of metallic materials. These alloys may be solidified and cooled at relatively slow rates, and they retain the amorphous, non-crystalline (i.e., glassy) state at room temperature. This amorphous state can be highly advantageous for certain applications. The fabrication of amorphous alloy can involve melting an alloy feedstock into a molten state and subsequently quenching the molten feedstock to create the final alloy form. Current methods to make the feedstock often involve compacting alloy powder into an ingot. However, the size of the feedstock ingot is usually small, as powder compaction does not result in a product of a large dimension. Further, often the feedstock is inhomogeneous with respect to chemical composition because the different chemical constituents do not have a chance to distribute homogenously. One consequence of localized inhomogeneity is a lack of an amorphous phase, as often amorphous alloys are sensitive to their chemical compositions. Also, such a limitation can be a challenge in the fabrication of an amorphous alloy as a structural component, as the part usually needs ingots of a relatively large size, compared to powder compact.

Thus, a need exists to develop methods that can fabricate feedstock that can be used to fabricate bulk amorphous alloy, the feedstock being homogenous and of a fairly large dimension.

SUMMARY

One embodiment provides a method of making an alloy feedstock, comprising: forming a first composition by combining Fe with a first nonmetal element; forming a second composition by combining Fe with a plurality of transition metal elements; forming a third composition by combining the second composition with a second nonmetal element; and combining the first composition with the third composition to form an alloy feedstock.

An alternative embodiment provides a method of making an alloy feedstock, comprising: forming a first composition by combining Fe with a first nonmetal element; forming a carbon-containing composition by combining Fe with a plurality of transition metal elements and C; combining the first composition with the carbon-containing composition to form an alloy feedstock.

Another embodiment provides a method of making an alloy feedstock, comprising: providing a Fe-containing first composition; combining C with a second composition comprising Mo, Cr, and Y to form a third composition; and combining the first composition with the third composition to form an alloy feedstock.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a schematic illustration of a pre-alloy composition formed during an intermediate step of a method in one embodiment. The composition has a certain stacking order that is found to provide surprising desirable results.

FIG. 2 provides an alternative view of the stacking order of the pre-alloy composition as described in FIG. 1.

FIG. 3 provides a schematic illustration for the formation of another pre-alloy in one embodiment, wherein another pre-alloy composition is placed on top of carbon particles to allow formation of a distinct carbon-containing pre-alloy composition from the pre-alloy and the carbon.

FIG. 4 shows a photograph of the different elements used for the alloying process and their relative dimension (to a ruler) in one embodiment—the non-powder pieces all have at least one dimension that is on the order of 5 mm or larger.

FIG. 5 shows a photograph of a Fe—Mo—Cr master alloy (or pre-alloy composition) ingot in one embodiment.

FIGS. 6( a)-6(b) shows the alloy ingot obtained in a comparative testing in one embodiment, with all the fractured pieces separated and the soot collected.

FIG. 7 shows a photograph of the alloy ingot obtained during a comparative testing in one embodiment, wherein the ingot is brittle, and fractured into many small pieces upon cooling.

FIGS. 8( a)-8(c) show the alloy feedstock made in accordance with one present embodiment and the amorphous alloy that is made from the feedstock by additional remelting and casting.

FIGS. 9( a)-(b) show two DSC thermograms taken from 6 mm and 8 mm cast rods, respectively, produced from the feedstock obtained in one presently described embodiment.

DETAILED DESCRIPTION Phase

The term “phase” herein can refer to one that can be found in a thermodynamic phase diagram. A phase is a region of space (e.g., a thermodynamic system) throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, chemical composition and lattice periodicity. A simple description is that a phase is a region of material that is chemically uniform, physically distinct, and/or mechanically separable. For example, in a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air over the water is a third phase. The glass of the jar is another separate phase. A phase can refer to a solid solution, which can be a binary, tertiary, quaternary, or more, solution, or a compound, such as an intermetallic compound. As another example, an amorphous phase is distinct from a crystalline phase.

Metal, Transition Metal, and Non-Metal

The term “metal” refers to an electropositive chemical element. The term “element” in this Specification refers generally to an element that can be found in a Periodic Table. Physically, a metal atom in the ground state contains a partially filled band with an empty state close to an occupied state. The term “transition metal” is any of the metallic elements within Groups 3 to 12 in the Periodic Table, that have an incomplete inner electron shell and serve as transitional links between the most and the least electropositive in a series of elements. Transition metals are characterized by multiple valences, colored compounds, and the ability to form stable complex ions.

The term “nonmetal” refers to a chemical element that does not have the capacity to lose electrons and form a positive ion. Depending on the application, any suitable nonmetal elements, or their combinations, can be used. The alloy composition can comprise multiple nonmetal elements, such as at least two, at least three, at least four, or more, nonmetal elements. A nonmetal element can be any element that is found in Groups 13-17 in the Periodic Table. For example, a nonmetal element can be any one of F, Cl, Br, I, At, O, S, Se, Te, Po, N, P, As, Sb, Bi, C, Si, Ge, Sn, Pb, and B. Occasionally, a nonmetal element can also refer to certain metalloids in Groups 13-17.

In some embodiments, metalloids are the elements found along the stair-step line that distinguishes metals from non-metals in the Period Table. This line is drawn from between boron and aluminum to the border between polonium and astatine. Metalloids have properties of both metals and non-metals. Some of the metalloids, such as silicon and germanium, are semi-conductors—for example, they can carry an electrical charge under special conditions. Some commonly known metalloids can include at least one metalloid, such as B, Si, Ge, As, Sb, Te, and Po. In one embodiment, the nonmetal elements can include B, Si, C, P, or combinations thereof. Accordingly, for example, the alloy composition can comprise a boride, a carbide, or both.

A transition metal element can be any of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, ununnilium, unununium, and ununbium. In one embodiment, a BMG containing a transition metal element can have at least one of Sc, Y, La, Ac, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, and Hg. Depending on the application, any suitable transitional metal elements, or their combinations, can be used. The alloy composition can comprise multiple transitional metal elements, such as at least two, at least three, at least four, or more, transitional metal elements.

The presently described alloy or alloy “sample” or “specimen” alloy can have any shape or size. For example, the alloy can have a shape of a particulate, which can have a shape such as spherical, ellipsoid, wire-like, rod-like, sheet-like, flake-like, or an irregular shape. The particulate can have any suitable size. For example, it can have an average diameter of between about 1 micron and about 100 microns, such as between about 5 microns and about 80 microns, such as between about 10 microns and about 60 microns, such as between about 15 microns and about 50 microns, such as between about 15 microns and about 45 microns, such as between about 20 microns and about 40 microns, such as between about 25 microns and about 35 microns. For example, in one embodiment, average diameter of the particulate is between about 25 microns and about 44 microns. In some embodiments, smaller particulates, such as those in the nanometer range, or larger particulates, such as those bigger than 100 microns, can be used.

The alloy sample or specimen can also be of a much larger dimension. For example, it can be a bulk structural component, such as an ingot, housing/casing of an electronic device or even a portion of a structural component that has dimensions in the millimeter, centimeter, or meter range.

Solid Solution

The term “solid solution” refers to a solid form of a solution. The term “solution” refers to a mixture of two or more substances, which may be solids, liquids, gases, or a combination of these. The mixture can be homogeneous or heterogeneous. The term “mixture” is a composition of two or more substances that are combined with each other and generally capable of being separated. Generally, the two or more substances are not chemically combined with each other.

Alloy

In some embodiments, the alloy composition described herein can be fully alloyed. In one embodiment, an “alloy” refers to a homogeneous mixture or solid solution of two or more metals, the atoms of one replacing or occupying interstitial positions between the atoms of the other; for example, brass is an alloy of zinc and copper. An alloy, in contrast to a composite or an intermetallic compound, can refer to a partial or complete solid solution of one or more elements in a metal matrix. The term “alloy” herein can refer to both a complete solid solution alloy that can give single solid phase microstructure and a partial solution that can give two or more phases.

Thus, a fully alloyed alloy can have a homogenous distribution of the constituents, be it a solid solution phase, a compound phase, or both. The term “fully alloyed” used herein can account for minor variations within the error tolerance. For example, it can refer to at least 90% alloyed, such as at least 95% alloyed, such as at least 99% alloyed, such as at least 99.5% alloyed, such as at least 99.9% alloyed. The percentage herein can refer to either volume percent or weight percentage, depending on the context. These percentages can be balanced by impurities, which can be in terms of composition or phases that are not a part of the alloy.

Amorphous or Non-Crystalline Solid

An “amorphous” or “non-crystalline solid” is a solid that lacks lattice periodicity, which is characteristic of a crystal. As used herein, an “amorphous solid” includes “glass” which is an amorphous solid that softens and transforms into a liquid-like state upon heating through the glass transition phase. Generally, amorphous materials lack the long-range order characteristic of a crystal, though they can possess some short-range order at the atomic length scale due to the nature of chemical bonding. The distinction between amorphous solids and crystalline solids can be made based on lattice periodicity as determined by structural characterization techniques such as x-ray diffraction and transmission electron microscopy.

The terms “order” and “disorder” designate the presence or absence of some symmetry or correlation in a many-particle system. The terms “long-range order” and “short-range order” distinguish order in materials based on length scales.

The strictest form of order in a solid is lattice periodicity: a certain pattern (the arrangement of atoms in a unit cell) is repeated again and again to form a translationally invariant tiling of space. This is the defining property of a crystal. Possible symmetries have been classified in 14 Bravais lattices and 230 space groups.

Lattice periodicity implies long-range order. If only one unit cell is known, then by virtue of the translational symmetry it is possible to accurately predict all atomic positions at arbitrary distances. The converse is generally true, except, for example, in quasi-crystals that have perfectly deterministic tilings but do not possess lattice periodicity.

Long-range order characterizes physical systems in which remote portions of the same sample exhibit correlated behavior. This can be expressed as a correlation function, namely the spin-spin correlation function: G(χ, χ′)=(s(χ), s(χ′)).

In the above function, s is the spin quantum number and x is the distance function within the particular system. This function is equal to unity when x=x′ and decreases as the distance |x−′| increases. Typically, it decays exponentially to zero at large distances, and the system is considered to be disordered. If, however, the correlation function decays to a constant value at large |x−x′|, then the system can be said to possess long-range order. If it decays to zero as a power of the distance, then it can be called quasi-long-range order. Note that what constitutes a large value of |x−x′| is relative.

A system can be said to present quenched disorder when some parameters defining its behavior are random variables that do not evolve with time (i.e., they are quenched or frozen)—e.g., spin glasses. It is opposite to annealed disorder, where the random variables are allowed to evolve themselves. Embodiments herein include systems comprising quenched disorder.

The alloy described herein can be crystalline, partially crystalline, amorphous, or substantially amorphous. For example, the alloy sample/specimen can include at least some crystallinity, with grains/crystals having sizes in the nanometer and/or micrometer ranges. Alternatively, the alloy can be substantially amorphous, such as fully amorphous.

In one embodiment, the presence of a crystal or a plurality of crystals in an otherwise amorphous alloy can be construed as a “crystalline phase” therein. The degree of crystallinity (or “crystallinity” for short in some embodiments) of an alloy can refer to the amount of the crystalline phase present in the alloy. The degree can refer to, for example, a fraction of crystals present in the alloy. The fraction can refer to volume fraction or weight fraction, depending on the context. A measure of how “amorphous” an amorphous alloy is can be amorphicity. Amorphicity can be measured in terms of a degree of crystallinity. For example, in one embodiment, an alloy having a low degree of crystallinity can be said to have a high degree of amorphicity. In one embodiment, for example, an alloy having 60 vol % crystalline phase can have a 40 vol % amorphous phase.

Amorphous Alloy or Amorphous Metal

An “amorphous alloy” is an alloy having an amorphous content of more than 50% by volume, preferably more than 90% by volume of amorphous content, more preferably more than 95% by volume of amorphous content, and most preferably more than 99% to almost 100% by volume of amorphous content. Note that, as described above, an alloy high in amorphicity is equivalently low in degree of crystallinity. An “amorphous metal” is an amorphous metal material with a disordered atomic-scale structure. In contrast to most metals, which are crystalline and therefore have a highly ordered arrangement of atoms, amorphous alloys are non-crystalline. Materials in which such a disordered structure is produced directly from the liquid state during cooling are sometimes referred to as “glasses.” Accordingly, amorphous metals are commonly referred to as “metallic glasses” or “glassy metals.” In one embodiment, a “bulk metallic glass” (“BMG”) can refer to an alloy, of which the microstructure is at least partially amorphous. However, there are several ways besides extremely rapid cooling to produce amorphous metals, including physical vapor deposition, solid-state reaction, ion irradiation, melt spinning, and mechanical alloying. Amorphous alloys can be a single class of materials, regardless of how they are prepared.

Amorphous metals can be produced through a variety of quick-cooling methods. For instance, amorphous metals can be produced by sputtering molten metal onto a spinning metal disk. The rapid cooling, on the order of millions of degrees a second, can be too fast for crystals to form, and the material is thus “locked in” a glassy state. Also, amorphous metals/alloys can be produced with critical cooling rates low enough to allow formation of amorphous structure in thick layers—e.g., bulk metallic glasses.

The terms “bulk metallic glass” (“BMG”), bulk amorphous alloys, and bulk solidifying amorphous alloys are used interchangeably herein. They refer to amorphous alloys having the smallest dimension at least in the millimeter range. For example, the dimension can be at least about 0.5 mm, such as at least about 1 mm, such as at least about 2 mm, such as at least about 4 mm, such as at least about 5 mm, such as at least about 6 mm, such as at least about 8 mm, such as at least about 10 mm, such as at least about 12 mm. Depending on the geometry, the dimension can refer to the diameter, radius, thickness, width, length, etc. A BMG can also be a metallic glass having at least one dimension in the centimeter range, such as at least about 1.0 cm, such as at least about 2.0 cm, such as at least about 5.0 cm, such as at least about 10.0 cm. In some embodiments, a BMG can have at least one dimension at least in the meter range. A BMG can take any of the shapes or forms described above, as related to a metallic glass. Accordingly, a BMG described herein in some embodiments can be different from a thin film made by a conventional deposition technique in one important aspect—the former can be of a much larger dimension than the latter.

Amorphous metals can be an alloy rather than a pure metal. The alloys may contain atoms of significantly different sizes, leading to low free volume (and therefore having viscosity up to orders of magnitude higher than other metals and alloys) in a molten state. The viscosity prevents the atoms from moving enough to form an ordered lattice. The material structure may result in low shrinkage during cooling and resistance to plastic deformation. The absence of grain boundaries, the weak spots of crystalline materials in some cases, may, for example, lead to better resistance to wear and corrosion. In one embodiment, amorphous metals, while technically glasses, may also be much tougher and less brittle than oxide glasses and ceramics.

Thermal conductivity of amorphous materials may be lower than that of their crystalline counterparts. To achieve formation of an amorphous structure even during slower cooling, the alloy may be made of three or more components, leading to complex crystal units with higher potential energy and lower probability of formation. The formation of amorphous alloy can depend on several factors: the composition of the components of the alloy; the atomic radius of the components (preferably with a significant difference of over 12% to achieve high packing density and low free volume); and the negative heat of mixing the combination of components, inhibiting crystal nucleation and prolonging the time the molten metal stays in a supercooled state. However, as the formation of an amorphous alloy is based on many different variables, it can be difficult to make a prior determination of whether an alloy composition would form an amorphous alloy.

Amorphous alloys, for example, of boron, silicon, phosphorus, and other glass formers with magnetic metals (iron, cobalt, nickel) may be magnetic, with low coercivity and high electrical resistance. The high resistance leads to low losses by eddy currents when subjected to alternating magnetic fields, a property useful, for example, as transformer magnetic cores.

Amorphous alloys may have a variety of potentially useful properties. In particular, they tend to be stronger than crystalline alloys of similar chemical composition, and they can sustain larger reversible (“elastic”) deformations than crystalline alloys. Amorphous metals derive their strength directly from their non-crystalline structure, which can have none of the defects (such as dislocations) that limit the strength of crystalline alloys. For example, one modem amorphous metal, known as Vitreloy™, has a tensile strength that is almost twice that of high-grade titanium. In some embodiments, metallic glasses at room temperature are not ductile and tend to fail suddenly when loaded in tension, which limits the material applicability in reliability-critical applications, as the impending failure is not evident. Therefore, to overcome this challenge, metal matrix composite materials having a metallic glass matrix containing dendritic particles or fibers of a ductile crystalline metal can be used. Alternatively, a BMG low in element(s) that tend to cause embitterment (e.g., Ni) can be used. For example, a Ni-free BMG can be used to improve the ductility of the BMG.

Another useful property of bulk amorphous alloys is that they can be true glasses; in other words, they can soften and flow upon heating. This allows for easy processing, such as by injection molding, in much the same way as polymers. As a result, amorphous alloys can be used for making sports equipment, medical devices, electronic components and equipment, and thin films. Thin films of amorphous metals can be deposited as protective coatings via a high velocity oxygen fuel technique.

A material can have an amorphous phase, a crystalline phase, or both. The amorphous and crystalline phases can have the same chemical composition and differ only in the microstructure—i.e., one amorphous and the other crystalline. Microstructure in one embodiment refers to the structure of a material as revealed by a microscope at 25× magnification or higher. Alternatively, the two phases can have different chemical compositions and microstructures. For example, a composition can be partially amorphous, substantially amorphous, or completely amorphous.

As described above, the degree of amorphicity (and conversely the degree of crystallinity) can be measured by the fraction of crystals present in the alloy. The degree can refer to volume fraction of weight fraction of the crystalline phase present in the alloy. A partially amorphous composition can refer to a composition of at least about 5 vol % of which is of an amorphous phase, such as at least about 10 vol %, such as at least about 20 vol %, such as at least about 40 vol %, such as at least about 60 vol %, such as at least about 80 vol %, such as at least about 90 vol %. The terms “substantially” and “about” have been defined elsewhere in this application. Accordingly, a composition that is at least substantially amorphous can refer to one of which at least about 90 vol % is amorphous, such as at least about 95 vol %, such as at least about 98 vol %, such as at least about 99 vol %, such as at least about 99.5 vol %, such as at least about 99.8 vol %, such as at least about 99.9 vol %. In one embodiment, a substantially amorphous composition can have some incidental, insignificant amount of crystalline phase present therein.

In one embodiment, an amorphous alloy composition can be homogeneous with respect to the amorphous phase. A substance that is uniform in composition is homogeneous. This is in contrast to a substance that is heterogeneous. The term “composition” refers to the chemical composition and/or microstructure in the substance. A substance is homogeneous when a volume of the substance is divided in half and both halves have substantially the same composition. For example, a particulate suspension is homogeneous when a volume of the particulate suspension is divided in half and both halves have substantially the same volume of particles. However, it might be possible to see the individual particles under a microscope. Another example of a homogeneous substance is air where different ingredients therein are equally suspended, though the particles, gases and liquids in air can be analyzed separately or separated from air.

A composition that is homogeneous with respect to an amorphous alloy can refer to one having an amorphous phase substantially uniformly distributed throughout its microstructure. In other words, the composition macroscopically comprises a substantially uniformly distributed amorphous alloy throughout the composition. In an alternative embodiment, the composition can be of a composite, having an amorphous phase having therein a non-amorphous phase, or vice versa. The non-amorphous phase can be a crystal or a plurality of crystals. The crystals can be in the form of particulates of any shape, such as spherical, ellipsoid, wire-like, rod-like, sheet-like, flake-like, or an irregular shape. In one embodiment, it can have a dendritic form. For example, an at least partially amorphous composite composition can have a crystalline phase in the shape of dendrites dispersed in an amorphous phase matrix; the dispersion can be uniform or non-uniform, and the amorphous phase and the crystalline phase can have the same or a different chemical composition. In one embodiment, they have substantially the same chemical composition. In another embodiment, the crystalline phase can be more ductile than the BMG phase.

The methods described herein can be applicable to any type of amorphous alloys. Similarly, the amorphous alloys described herein as a constituent of a composition or article can be of any type. The amorphous alloy can comprise the element Zr, Hf, Ti, Cu, Ni, Pt, Pd, Fe, Mg, Au, La, Ag, Al, Mo, Nb, Be, or combinations thereof. Namely, the alloy can include any combination of these elements in its chemical formula or chemical composition. The elements can be present at different weight or volume percentages. For example, an iron “based” alloy can refer to an alloy having a non-insignificant weight percentage of iron present therein, the weight percent can be, for example, at least about 40 wt %, such as at least about 50 wt %, such as at least about 60 wt %, such as at least about 80 wt %. Alternatively, in one embodiment, the above-described percentages can be volume percentages, instead of weight percentages. Accordingly, an amorphous alloy can be zirconium-based, titanium-based, platinum-based, palladium-based, gold-based, silver-based, copper-based, iron-based, nickel-based, aluminum-based, molybdenum-based, and the like. In some embodiments, the alloy, or the composition including the alloy, can be substantially free of nickel, aluminum, or beryllium, or combinations thereof. In one embodiment, the alloy or the composite is completely free of nickel, aluminum, or beryllium, or combinations thereof.

For example, the amorphous alloy can have the formula (Zr, Ti)_(a)(Ni, Cu, Fe)_(b)(Be, Al, Si, B)_(c), wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 30 to 75, b is in the range of from 5 to 60, and c is in the range of from 0 to 50 in atomic percentages. Alternatively, the amorphous alloy can have the formula (Zr, Ti)_(a)(Ni, Cu)_(b)(Be)_(c), wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 40 to 75, b is in the range of from 5 to 50, and c is in the range of from 5 to 50 in atomic percentages. The alloy can also have the formula (Zr, Ti)_(a)(Ni, Cu)_(b)(Be)_(c), wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 45 to 65, b is in the range of from 7.5 to 35, and c is in the range of from 10 to 37.5 in atomic percentages. Alternatively, the alloy can have the formula (Zr)_(a)(Nb, Ti)_(b)(Ni, Cu)_(c)(Al)_(d), wherein a, b, c, and d each represents a weight or atomic percentage. In one embodiment, a is in the range of from 45 to 65, b is in the range of from 0 to 10, c is in the range of from 20 to 40 and d is in the range of from 7.5 to 15 in atomic percentages. One exemplary embodiment of the aforedescribed alloy system is a Zr—Ti—Ni—Cu—Be based amorphous alloy under the trade name Vitreloy™, such as Vitreloy-1 and Vitreloy-101, as fabricated by Liquidmetal Technologies, CA, USA. Some examples of amorphous alloys of the different systems are provided in Table 1.

The amorphous alloys can also be ferrous alloys, such as (Fe, Ni, Co) based alloys. Examples of such compositions are disclosed in U.S. Pat. Nos. 6,325,868; 5,288,344; 5,368,659; 5,618,359; and 5,735,975, Inoue et al., Appl. Phys. Lett., Volume 71, p 464 (1997), Shen et al., Mater. Trans., JIM, Volume 42, p 2136 (2001), and Japanese Patent Application No. 200126277 (Pub. No. 2001303218 A). One exemplary composition is Fe₇₂Al₅Ga₂P₁₁C₆B₄. Another example is Fe₇₂Al₇Zr₁₀Mo₅W₂B₁₅. Another iron-based alloy system that can be used in the coating herein is disclosed in U.S. Patent Application Publication No. 2010/0084052, wherein the amorphous metal contains, for example, manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon (0.3 to 3.1 atomic %) in the range of composition given in parentheses; and that contains the following elements in the specified range of composition given in parentheses: chromium (15 to 20 atomic %), molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to 16 atomic %), carbon (3 to 16 atomic %), and the balance iron.

The aforedescribed amorphous alloy systems can further include additional elements, such as additional transition metal elements, including Nb, Cr, V, and Co. The additional elements can be present at less than or equal to about 30 wt %, such as less than or equal to about 20 wt %, such as less than or equal to about 10 wt %, such as less than or equal to about 5 wt %. In one embodiment, the additional, optional element is at least one of cobalt, manganese, zirconium, tantalum, niobium, tungsten, yttrium, titanium, vanadium and hafnium to form carbides and further improve wear and corrosion resistance. Further optional elements may include phosphorous, germanium and arsenic, totaling up to about 2%, and preferably less than 1%, to reduce melting point. Otherwise incidental impurities should be less than about 2% and preferably 0.5%.

In some embodiments a composition having an amorphous alloy can include a small amount of impurities. The impurity elements can be intentionally added to modify the properties of the composition, such as improving the mechanical properties (e.g., hardness, strength, fracture mechanism, etc.) and/or improving the corrosion resistance. Alternatively, the impurities can be present as inevitable, incidental impurities, such as those obtained as a byproduct of processing and manufacturing. The impurities can be less than or equal to about 10 wt %, such as about 5 wt %, such as about 2 wt %, such as about 1 wt %, such as about 0.5 wt %, such as about 0.1 wt %. In some embodiments, these percentages can be volume percentages instead of weight percentages. In one embodiment, the alloy sample/composition consists essentially of the amorphous alloy (with only a small incidental amount of impurities). In another embodiment, the composition consists of the amorphous alloy (with no observable trace of impurities).

TABLE 1 Exemplary amorphous alloy compositions Alloy Atm % Atm % Atm % Atm % Atm % Atm % 1 Zr Ti Cu Ni Be 41.20% 13.80% 12.50%  10.00% 22.50% 2 Zr Ti Cu Ni Be 44.00% 11.00% 10.00%  10.00% 25.00% 3 Zr Ti Cu Ni Nb Be 56.25% 11.25% 6.88%  5.63%  7.50% 12.50% 4 Zr Ti Cu Ni Al Be 64.75%  5.60% 14.90%  11.15%  2.60%  1.00% 5 Zr Ti Cu Ni Al 52.50%  5.00% 17.90%  14.60% 10.00% 6 Zr Nb Cu Ni Al 57.00%  5.00% 15.40%  12.60% 10.00% 7 Zr Cu Ni Al Sn 50.75% 36.23% 4.03%  9.00%  0.50% 8 Zr Ti Cu Ni Be 46.75%  8.25% 7.50% 10.00% 27.50% 9 Zr Ti Ni Be 21.67% 43.33% 7.50% 27.50% 10 Zr Ti Cu Be 35.00% 30.00% 7.50% 27.50% 11 Zr Ti Co Be 35.00% 30.00% 6.00% 29.00% 12 Au Ag Pd Cu Si 49.00% 5.50% 2.30% 26.90% 16.30% 13 Au Ag Pd Cu Si 50.90% 3.00% 2.30% 27.80% 16.00% 14 Pt Cu Ni P 57.50% 14.70% 5.30% 22.50% 15 Zr Ti Nb Cu Be 36.60% 31.40% 7.00%  5.90% 19.10% 16 Zr Ti Nb Cu Be 38.30% 32.90% 7.30%  6.20% 15.30% 17 Zr Ti Nb Cu Be 39.60% 33.90% 7.60%  6.40% 12.50% 18 Cu Ti Zr Ni 47.00% 34.00% 11.00%   8.00% 19 Zr Co Al 55.00% 25.00% 20.00% 

Alloy Feedstock Fabrication

The presently described methods can involve making of an alloy feedstock that can be subsequently used to fabricate a BMG. The BMG can be of any of the aforementioned alloy compositions. In one embodiment, the BMG is a ferrous alloy, such as a Fe-based alloy. In one embodiment, the alloy can have a chemical formula of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂. Note that many other Fe-based alloys are also possible. The alloy feedstock can have the same chemical composition as the final BMG, although this need not be the case. In one embodiment, the alloy feedstock has the same in chemical composition as the BMG that is subsequently manufactured but has different degree of crystallinity. For example, in one embodiment, the alloy feedstock can be not fully amorphous, such as substantially crystalline, such as fully crystalline.

In one embodiment, the method of making an alloy feedstock can comprise at least two steps, each of which involves making a pre-alloy composition. The pre-alloy compositions from the different steps can be the same or different. Although the final product (i.e., the alloy feedstock) produced according to the presently described methods in some embodiments can be homogeneous alloys, the “pre-alloy composition” referred to herein need not be an alloy or homogenous. For example, in one embodiment, the any of the pre-alloy compositions can be a compound, such as an intermetallic compound. Alternatively, the composition can be a mixture. Further, in some embodiments, the pre-alloy compositions and/or the alloy feedstock are homogeneous with respect to chemical composition. However, the pre-alloy compositions, or even the alloy feedstock, need not be fully homogeneous particularly with respect to chemical composition. For example, they can be homogeneous in a certain portion thereof but not other portions thereof. Alternatively, they can be not homogenous.

In one embodiment, a method of making an alloy feedstock is provided, the method can include several intermediate steps. For example, the method can involve forming a series of pre-alloys that can be subsequently combined. The method can involve forming a first composition by combining Fe element with a first nonmetal element; forming a second composition by combining Fe with a plurality of transition metal elements; forming a third composition by combining the second composition with a second nonmetal element; and alloying the first composition with the third composition to form an alloy feedstock. In one embodiment, the alloy feedstock comprises a ferrous alloy, such as a Fe-containing alloy, such as a Fe-based alloy. The elements can be of any size or shape. In contrast to the pre-existing methods that rely on powder compaction, at least some of the elements used in the presently described embodiments have at least one dimension much larger than general “powder” dimension—e.g., in the millimeter scale or larger, such as at least about 1 mm, such as at least about 2 mm, such as at least about 2 mm, such as at least about 5 mm. In one embodiment, all of the elements have at least one dimension in the millimeter scale or larger. In another embodiment, this dimension refers to the smallest dimension.

In one embodiment, the first pre-alloy composition can be a Fe-containing composition, such as a compound, such as an intermetallic compound in one embodiment. The first pre-alloy composition can alternatively be an alloy such as a Fe-containing alloy. The nonmetal element can be any of the aforementioned metalloids. For example, it can be B, P, Si, Ge, C, or a combination thereof. Accordingly, the first composition can comprise iron boride, iron phosphide, etc. For example, the first composition can include Fe₂B, FeB, FeSi, FeSi₂, Fe₃P, or combinations thereof. In some embodiments, these compounds can be generally available as coarse powder, such as commercially available powder. Alternatively, they can be “chunk” of a larger dimension—e.g., in millimeter scale as aforementioned. In one embodiment, the element C (and others) can be added or incorporated through the use of alloy, such as white or gray cast iron, which generally can have compositions containing Fe, C, Si, and small amounts of other elements. In some alternative embodiments, instead of using pre-existing compounds and alloys, the manual pre-alloying steps described herein can be used to combine various elements, compounds, and/or alloys to form master alloys/pre-alloys on site. An example can be a Fe—Cr—Mo ingot described herein and in the Non-limiting Working Examples section or the Fe—B master alloy ingot described herein. See FIG. 5.

The second pre-alloy composition can comprise a plurality of transition metal elements. The transition metal elements can be any combinations of the aforementioned transition metal elements. In one embodiment, the elements can include at least one of Fe, Mo, Cr, Ni, Y, Co, Mn, Ga, and Er. In one embodiment, the second composition can comprise Fe, Mo, Cr, Y, Co, Mn, Ga, and Er. In another embodiment, the composition can consist essentially of Fe, Mo, Cr, Y, Co, Mn, Ga, and Er. In one embodiment, the second composition can consist of Fe, Mo, Cr, Y, Co, Mn, Ga, and Er.

The second nonmetal element can also be any of the nonmetals, including the metalloids described above. For example, it can be C, or it can be B or P as the first metalloid. Carbon element can be supplied in the form of graphite, or any other suitable carbon sources. The transition metal elements can be stacked in a certain order during this melting/alloying. In some embodiments, the stack order can be surprisingly important. Specifically, in some embodiments, a different stack order than what is described herein may result in alloy feedstock having inferior property, if any feedstock can be produced at all. For example, in one embodiment the forming surprisingly can have a lower evaporation of at least one of Fe and Cr for the second pre-alloy composition relative to a composition not with the stack order. The evaporation of elements can be undesirable in some embodiments because of the loss of the elements thus the increase in reduction time and/or cost.

In one embodiment, the stack order can be Mo disposed over Fe, which is disposed over Cr, which is disposed over Y, as shown in FIG. 1. Note that the order therein is merely illustrative, and can be, for example, reversed if the composition is put up-side-down. The stack order can also be perpendicular to what is shown in FIG. 1. For example, it can be from left to right, or alternatively, right to left. In one embodiment, Mo can have the highest melting temperature among all of the four elements. FIG. 5 shows an image of a Fe—Mo—Cr master alloy (or pre-alloy) ingot in one embodiment. The ingot can be homogeneous with respect to the constituents, but it need not be the case in all embodiments. Not to be bound by any particular theory, but Mo can serve as a temporary shield for the other elements to lower the possibility of thermal shock. During this alloying/combining step, the individual elements can melt and fuse with another in any particular sequence. For example, in this embodiment, Fe can first fuse with Mo, and Cr can then fuse with the intermediate Fe—Mo composition; finally, Y can fuse with the Fe—Mo—Cr composition. Accordingly, by the time Y is fused with the other elements to form this second pre-alloy composition, the pre-alloy composition can be already homogeneous with respect to these elements. Alternatively, in another embodiments, the second pre-alloy need not be homogeneous.

In one embodiment, as the combination of elements increases in temperature and mixes, it can blend into a homogenous liquid with some degree of surface tension. The surface tension can tend to pull the molten blob into a roughly circular ingot (or a “button”), while the force of gravity can tend to flatten it out. Depending on the size of the ingot, as it becomes homogenous it will thus form into a disc shape with rounded off edges, and the transition from disparate heated chunks to a rounded blob of homogenous alloy can be clearly observed during the arc melting process. In some incidences this transition is referred to as “rounded out”.

In one embodiment, at the beginning of the forming the third composition, the second nonmetal element can be placed under the second composition. In one embodiment, the third pre-alloy composition can be formed by combining the second nonmetal element with the second composition. For example, if the second nonmetal element is carbon, the third composition can be a carbon-containing composition. The combination can take place in any configuration. For example, the carbon can be in the form of a plurality of particulates, such as graphite particles. The particles can be placed under the second pre-alloy composition before the melting/alloy step. Alternatively, the carbon can be placed on the top or side(s) of the second pre-alloy composition. In one embodiment, the third pre-alloy composition can comprise a Fe—Mo—Cr—Y—C alloy or a composition comprising these elements. Note that the order of the element symbols in the alloys described herein can be changed without changing the meaning of the alloy.

The melting and alloying described here can be carried out by any suitable heating techniques. For example, the heating can involve arc melting, vacuum induction melting (VIM), flash lamp, resistance furnace, laser, electron beam, or combinations thereof. After (and in between) each melting/combining step, the pre-alloy composition can be cooled to a lower temperature, such as room temperature. Depending on the composition and the melting technique used, each of the combining steps in the methods described herein can vary in length (of time). In one embodiment, at least some of the combining steps can take about at least 10 minutes, such as at least about 20 minutes, such as at least about 30 minutes. Accordingly, in one embodiment, the entire making process of the alloy feedstock can take about at least 1 hour, such as at least about 1.5 hours, such as at least 2 hours. The term combining herein for any of the pre-alloy forming steps can refer to any type of combination, including physical combination and/or chemical combination. For example, combining can refer to alloying and/or mixing a plurality of elements, such as during melting. Alternatively, depending on the context, combining can refer to chemically forming a new compound.

In one embodiment wherein the heating is carried out by arc-melting, during melting the alloy charge or pre-alloy composition mixtures can be melted and/or flipped. In one embodiment, a “melt” in arc-melting can refer to a process of using an electrical arc to melt the (metal) elements and to fuse/mix them together. The arc can have the capability of penetrating the molten metal mixture and mix them together. In some embodiments, if the arc is moved in a certain pattern (or patterns), high homogeneity can be achieved. However, often there can be some un-melted chunk of metal that precipitate to the bottom of the melt (at the cold heart) and remain un-melted (e.g., in its pure/original form). In some incidences, the arc can then be stopped, letting the mixture cool down to form a solid, and then the mixture (or button or ingot) can be nipped from flipped just like flipping a pancake or over-easy egg. After the flip, the arc can be turned back on and the button can start to melt from the edge of the button and move across the button slowly. As time passes, the un-melted chunks can be found and the arc can be focused on these chunks to melt them into the mixture.

In some embodiments, a “flip” can also refer to tumbling the mixture to promote homogenization before each “melt” as described above For example, in one embodiment a “4 melts and 3 flip” can refer to the following sequence: melt, wait for solid, flip, melt, wait for solid, flip, melt, wait for solid, flip, and melt. In this embodiment, the higher-density un-melted metal/alloy chunk can sink to the bottom, while the lower-density un-melted chunk can stay afloat. In one embodiment, flipping can be carried out because the metals are melted on a water-cooled piece of copper. The bottom of the ingot can be near the temperature of the copper, while the top is heated directly by the arc. Thus, very often this means that the densest elements will not completely mix before they sink to the bottom, and when they sink to the bottom they are in a cooler region of the ingot—as a result, they stop dissolving. Therefore, in some embodiments, the entire ingot was let cooled and manually flipped over. Once the arc is turned back on, what used to be the bottom of the ingot can be heated, so that the inhomogeneities are dissolved more before they sink. Accordingly, the unmelted pieces embedded in the ingot can be reduced and the ingot can become more homogeneous with each subsequent flip and remelt.

The feedstock produced by the methods in some embodiments provided herein can be in the form of a button or ingot—these two terms can be used interchangeably in some embodiments described herein. The feedstock button or ingot can have any shape or size. For example, the ingot can be cylindrical, spherical, cubical, or having any shape in between or an irregular shape. The feedstock can also take any of the size or shape of the alloy sample as described previously. As described above, the feedstock can be homogeneous, particularly with respect to chemical composition. In some embodiments, the feedstock can be homogeneous throughout the entire feedstock. In some alternative embodiments, the feedstock can be homogeneous only in certain regions therein—i.e., the feedstock only has localized homogeneity and no bulk homogeneity. Having high homogeneity is surprisingly important. The BMG, particularly the alloys described herein, can be very sensitive to chemical composition, and the inhomogeneity can cause an altered chemical compositions at different locations in the feedstock. Consequently, as shown below, the inhomogeneity can result in the presence of non-amorphous phase.

The feedstock can have a dimension that is in the millimeter range or larger, such as centimeter range or larger—this large dimension can be distinct from the feedstock that is produced by pre-existing powder compaction of different elements in powder form. In one embodiment, the feedstock can have at least one dimension that is at least about 1 cm, such as at least about 2 cm, such as at least about 4 cm, such as at least about 6 cm, such as at least about 8 cm, such as at least about 10 cm, such as at least about 12 cm. In one embodiment, the alloy feedstock can have at least one dimension that is at least 1 inch, such as at least 2 inches, such as at least 3 inches, such as at least about 4 inches. The dimension herein can refer to any dimension, such as length, width, thickness, diameter, etc.

The alloy feedstock made in accordance with the methods described herein can be used to fabricate amorphous alloys, such as bulk amorphous alloys. The methods of making amorphous alloys are known. For example, in one example the feedstock can be re-melted into a molten form and subsequently quenched to form amorphous alloys. The techniques of making amorphous alloy from crystalline alloys are known, and any of the known methods can be employed hereinto to fabricate the composition. Although different examples of methods of forming are described here, other similar forming processes or combinations thereof can also be used. In one embodiment, the feedstock is heated to a first temperature that is above the melting temperature Tm of the alloy in the feedstock such that any crystals in the alloy can be melted. The heated and melted feedstock can then be rapid-cooled (or “quenched”) to a second temperature that is below the Tg of the alloy to form the aforementioned composition, which can then be heated to be disposed and/or shaped. The rate of quenching and the temperature to be heated to can be determined by convention methods, such as utilizing a Time-Temperature-crystal Transformation (TTT) diagram. The provided sheets, shot, or any shape feedstock can have a small critical casting thickness, but the final part can have thickness that is either thinner or thicker than the critical casting thickness.

Electronic Device

The aforedescribed methods can be used to fabricate feedstock that can be subsequently used to make BMG. Because of the superior properties of BMG, BMG can be made into structural components in a variety of devices and parts. One such type of device is an electronic device.

An electronic device herein can refer to any electronic device known in the art. For example, it can be a telephone, such as a cell phone, and a land-line phone, or any communication device, such as a smart phone, including, for example an iPhone™, and an electronic email sending/receiving device. It can be a part of a display, such as a digital display, a TV monitor, an electronic-book reader, a portable web-browser (e.g., iPad™), and a computer monitor. It can also be an entertainment device, including a portable DVD player, conventional DVD player, Blue-Ray disk player, video game console, music player, such as a portable music player (e.g., iPod™), etc. It can also be a part of a device that provides control, such as controlling the streaming of images, videos, sounds (e.g., Apple TV™), or it can be a remote control for an electronic device. It can be a part of a computer or its accessories, such as the hard drive tower housing or casing, laptop housing, laptop keyboard, laptop track pad, desktop keyboard, mouse, and speaker. The article can also be applied to a device such as a watch or a clock.

The articles “a” and “an” are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “a polymer resin” means one polymer resin or more than one polymer resin. Any ranges cited herein are inclusive. The terms “substantially” and “about” used throughout this Specification are used to describe and account for small fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%.

NON-LIMITING WORKING EXAMPLES Fe-Based Alloys

For comparison, three experiments were conducted. The first two experiments were conducted following pre-eXisting protocols of making an alloy feedstock for later fabrication of a ferrous bulk amorphous alloy (Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂), and the third experiment was conducted using the method described in one of the present embodiments. The heating and melting described below were carried out by arc-melting. FIG. 4 shows a photograph of the elements used for the alloying process and their relative dimension to a ruler—the pieces all have at least one dimension that is on the order of 5 mm or larger.

Experiment 1

This experiment was conducted in an attempt to make an alloy feedstock according to the following protocol:

-   -   (1) Melt about 3.1 g of B (˜0.29 moles) and 16.0 g of Fe (˜0.29         moles) to make a 50-atm %-Fe-50-atm %-B (Fe—B) compound         composition. This step was performed with 4 melts and 3         flips—i.e., every “flip” refers to tumbling the mixture to         promote homogenization before each “melt” as described above.     -   (2) Melt about 112.3 g of Fe; 37.4 g of Cr; 64.2 g of Mo to form         a Fe—Cr—Mo alloy ingot (“button”). This step was performed with         4 melts and 3 flips. FIG. 5 provides a photograph of a Fe—Cr—Mo         alloy.     -   (3) Melt graphite into Fe—Mo—Cr by putting the FeCrMo ingot on         top of graphite particles to forming Fe—Mo—Cr—C composition.         This step was performed with 1 melt and no flips.

(4) Melt the Fe—B compound with Fe—Mo—Cr—C composition in an attempt to from an alloy feedstock with the chemical formula Fe₄₈Cr₁₅Mo₁₄B₆Y₂.

Results

The atomic (or volume) ratio of the elements were set to be Mo:C=48:52; Cr:C=50:50; Mo:B=70:30; and Cr:B=71:29. During step (1), Fe and B were found to fuse fairly quickly to form a viscous intermetallic compound composition. The power of the arc was then raised in order to fully melt the intermetallic composition. During the ramping up of the power, the relatively inhomogeneous pre-alloyed intermetallic composition mixed together completely and became homogenous, forming quickly into a rounded, molten ingot. A minimal amount of soot surrounding the intermetallic composition was found after the first and second melts.

During step (2), Fe melted readily and fused with Mo immediately. Cr was found to evaporate rapidly where Cr was in contact with the arc. The vapor pressure of pure Cr was very high comparing to pure Fe. Inside the arc melter, the Argon pressure was between −10 to −20 in-Hg. At this “vacuum” level, it was even easier for the Cr to evaporate. The walls, hearth, part of the electrode of the arc melter are kept cold via chilled water. As the evaporated Cr encountered a cold surface, it automatically precipitated and coated the walls, hearth, and the electrode. It was attempted to keep the Cr away from the arc to reduce evaporation and precipitation into colder surfaces of the equipment.

Another side effect of this phenomenon was a loss of the Cr to the equipment, resulting in the alloy having a decreased Cr concentration. If a thick enough layer of Cr were coated on the electrode and its seals or floating inside the arc melter's atmosphere, an electrical “short” could have happened and is dangerous. It was noted that when the arc (which resembles a diffuse flame pointing straight out of the tungsten tip) was aimed right onto a piece of Cr, evaporation became excessive. When it was aimed at a lower vapor pressure element, such as Mo, instead, and the Mo was allowed to heat up the Cr indirectly, evaporation is minimized. Lower than anticipated amount of soot was observed, and it was concluded that Cr should be kept away from the arc.

During step (3), the Fe—Cr—Mo ingot obtained from step (2) was put on top of carbon (graphite) particles. It was found that the Fe—Cr—Mo ingot was cracked, and the ingot was melted from the edge first to prevent shattering. The newly formed ingot Fe—Cr—Mo was crystalline. As it was lying on the cold hearth of the arc melter, the whole ingot was quite cold. When the hot arc current touched the ingot, thermal shock caused the ingot to crack. When it cracked, the debris could land anywhere inside the arc melter that can cause “bad composition”, “electrical short”. It is concluded that it is best to melt first from the edge to prevent cracking via thermal shock and also help find “un-melted” chunk and melt them. In some cases sudden heat caused large pieces to shatter in the arc melter. In the case of the Fe—Cr—Mo, the ingot also tended to fracture spontaneously as it cooled. Not to be bound by any theory, but it was probably because it cooled rapidly enough on the copper hearth that thermal shock also leads to fracture of the brittle intermetallics in the ingot.

It was found that pieces of C floated to the surface as soon as the ingot melted and that pieces of C glowed and darted around the surface then gradually disappeared. After a period of time, the entire ingot became molten and a thin scale covering 25-33% of the surface flowed around rapidly. Once the arc was reduced, a glowing, apparently immiscible glob of viscous material floated onto the top of the ingot. The arc pushed it around and caused it to flow and deform, but it refused to go into solution. No chemical analysis was performed to verify whether the solution was a solid solution. Lots of soot was observed, and a smell of something burnt was detected.

During step (4), Y and Fe—B composition from step (1) were put on top of the Fe—Cr—Mo—C ingot and the assembly was melted. Yttrium was found to dissolve rapidly into the ingot, while the Fe—B composition dissolved very reluctantly and slowly into the ingot. After the Fe—B melted, the resulting ingot gradually became covered with a rough, faceted scale that was not dissolved.

After the final ingot was cooled, the surface was found to have turned from dull, dark gray to white and had a smell that was similar to metallic sewage. Also, it was found that the final ingot was not able to be rendered fully molten during the melting—only localized molten regions were visible beneath the coarse scale. In other words, when the elements were mixed in the arc melter, one or more compounds formed on the surface, which had melting points higher than the ˜3400° C. maximum temperature that the arc melter was capable of tolerating. These high melting point compounds could not be subsequently dissolved back into the bulk of the button, potentially making the ingot inhomogeneous. Also, since only localized regions could be melted with the arc, the ingot was inhomogenous in composition.

FIG. 6( a) shows the alloy ingot that resulted from Experiment 1, with all the fractured pieces separated. There are some voids and inhomogeneity visible in the fracture surfaces. The ingot was fairly brittle, and fractured into multiple pieces upon cooling. Also, evaporation of some of the alloy constituents created a great deal of soot which was subsequently collected after cooling (shown on the right)—no determination was performed for the elements present in the soot. The soot collected after Experiment 1 is shown in FIG. 6( b). The surface of the ingot was rough and irregular and showed signs of inhomogeneity caused by incomplete mixing during the melting process.

In sum, the ingot is undesirable as a feedstock.

Experiment 2

This experiment was conducted in an attempt to make an alloy feedstock according to the following protocol:

-   -   (1) Melt about 128.1 g of Fe and about 4.9 g of C to make a         85-atm %-Fe-15-atm %-C (Fe—C) compound composition—the step was         performed with Fe on top of C. This step was performed with 4         melts and 3 flips—i.e., every “flip” refers to tumbling the         mixture to promote homogenization before each “melt” (i.e.,         melting).     -   (2) Melt about 3.7 g of C with about Cr, Mo, and B, with Mo         being on top of B being on top of Cr being on top of C. Based on         back calculation, it was determined that Cr ˜37.3 g; Mo ˜64.2 g;         B ˜3.1 g.     -   (3) Put Fe—C on top of Fe, Cr, Mo, and B and melt all of these         together to minimize Cr loss. The product was an ingot.     -   (4) 0.2 g of Y was added to the ingot obtained from (3) and the         assembly was melted together.

Results

During step (1), Fe melted slowly. When in contact with molten Fe, carbon arc glowed green, and molten alloy fizzed. When C floated to the top, it slowly dissolved into solution, skipping around the surface. Moderate soot generation, probably mostly due to the fizzing, was observed. The soot was found to include mainly a grey powder. This powder was collected and added to subsequent melting steps.

During step (2), it was found that Mo melted and fused with Cr to some extent, but substantial Cr boiled off before the mixture could be consolidated. During step (3), it was found that all of the mixture after mixing and melting eventually became homogenous. C pieces were seen to float to the top and dissolve slowly into solution. Also, in step (2), some Cr evaporated/boiled off. In step (3), additional Cr evaporated. Finally, during step (4), Y was found to fuse with the ingot, but it immediately formed a thick “skin” which was very difficult to melt. It was very difficult to melt the entire ingot at once. When something boiled off, it was lost, and thus the final composition was no longer the correct composition. When two or more elements clumped together to form crystal, no homogeneous mixture was obtained. When something floated or precipitated, no homogeneous mixture was obtained. For melting this particular Fe alloy composition, the Cr and the C gave a lot of problem. Even though C float on top, it dissolved slowly into the solution. On the other hand, if Cr was introduced into the alloy too early, the Cr evaporated off too much during the time it took for the C to dissolve.

FIG. 7 shows a photograph of the alloy ingot obtained in Experiment 2. The ingot was extremely brittle, and fractured into many small pieces upon cooling. Not as much soot as in Experiment 1 was observed, but the pieces were still covered with a light colored dust than in Experiment 1. Even more inhomogeneity than in Experiment 1 was observed in this Experiment, and the surface showed evidence of an immiscible skin. In sum, the ingot is undesirable to be used as a feedstock.

Experiment 3

This experiment was conducted in an attempt to make an alloy feedstock according to the following protocol:

-   -   (1) Melt about 12.8 g of Fe and about 2.5 g of C to make a         50-atm %-Fe-50-atm %-B (Fe—B) compound composition—the step was         performed with Fe on top of C. This step was carried out similar         to step (1) in Experiment 1.     -   (2) Melt about 98 g of Fe with about 29.8 g Cr; 51.4 g Mo; and         6.9 g Y, as shown in FIG. 2, to form FeMoCrY.     -   (3) Put C underneath each piece of Fe—Mo—Cr—Y to form an alloy         thereof. The product is an ingot.     -   (4) Feb from step (1) was melted into the Fe—Mo—Cr—Y pieces         obtained from step (3) to crate an alloy feedstock of         Fe₄₈Cr₁₅Mo₁₄B₆Y₂.

Results

During step (1), the results obtained were similar to those observed in step (1) in Experiment 1. Specifically, the elements became fused and viscous but formed an button/ingot after the power of arc melting was raised.

During step (2), Fe was found to fuse rapidly with Mo. See FIG. 2. Once Y was melted, the material formed a scale on its surface, and the scale would not melt even at high power. Small, orange drops of some immiscible material were found to roll around the surface, but they did not mix into the ingot even at high power. The ingot was so brittle that it broke when it fell back onto the hearth. A small piece was re-melted in trough; and during the re-melting, the scale looked much more sparse, almost seemed to be dissolving. It was concluded that melting the Fe—Mo—Cr—Y in smaller chunks helped with the melting process. A good amorphous alloy tends to have good surface appearance. Whereas the larger chunk of material could not be fully melted with the arc due to various factors (high melting point skin, apparently immiscible phases, etc.), splitting off a small piece and melting it separately showed that the skin could be at least partially dissolved into solution. Not to be bound by any theory, but this was probably because the small mass of that piece allowed for higher melting temperatures to be achieved with the same arc. After solidifying, the Fe—Mo—Cr—Y surface was faceted, with blue and brown colors.

During step (3), C appeared to dissolve slowly into each piece of material with no trouble. Carbon particles were put under the Fe—Mo—Cr—Y ingot, as shown in FIG. 3. Rather than floating to the surface, the mass of each Fe—Mo—Cr—Y piece “pinned” down the C rods in cool regions. Carbon is a lighter element (lower density), it has the tendency to float to top. If carbon were pinned down (i.e., trapped) below the Fe—Mo—Cr—Y, as the mixture was melted the carbon dissolved into the mixture slowly as it floated up gradually. By the time it reached the top, most of the C has been dissolved into the mixture. Also, because only localized regions of the ingot could be melted, the remaining regions of the ingot behaved like a solid. Thus, the carbon could not float up through the solid regions, and was stuck (or “pinned”) on the bottom, even when the arc was moved to generate a molten region above one end of the carbon rod. The part that was below the molten region slowly dissolved into solution without floating to the top at all. This minimized some of the inconsistency and effort associated with the process of dissolving the C into the alloy.

During step (4) the Fe—B composition was on top. After it melted, the composition initially did not wet the big pieces. After it rolled off the surface, it fused with the side of the Fe—Mo—Cr—Y and began to dissolve slowly into the bulk. As it became more homogenous, the resulting ingot appeared to become less viscous. The result product of this experiment includes ingots that are at least 100 g in weight and 2-3 inches in diameter. Post experimental verification shows that the ingot was used as a feedstock to produce fully amorphous BMG rods that are at least 5 mm in diameter.

FIG. 8( a) shows small homogenous but crystalline pieces retained from the ingot produced in Experiment 3 (top). Some pieces were remelted and suction-cast into a cold copper mold to produce the amorphous alloy cast shown at the bottom of FIG. 8( a). FIG. 8( b) shows a section from a 6 mm diameter rod cast made by remelting and suction casting pieces from Fe-based alloying Experiment 3. The rod was fully amorphous. FIG. 8( c) shows a section from an 8 mm diameter rod cast made by remelting and suction casting pieces from Fe-based alloying Experiment 3. The rod was fully amorphous.

The observation that the alloy rods made from the feedstock in Experiment 3 was confirmed by a series of DSC examination. FIGS. 9( a)-(b) show two DSC thermograms taken from the 6 mm and 8 mm cast rods, respectively, produced from the feedstock obtained from Experiment 3. FIG. 9( a) was obtained from the 6 mm rod cast, while FIG. 9( b) shows results from both the 6 and 8 mm rods in the same chart. The similarity of the curves, particularly the crystallization event between 600 and 800° C., illustrates that the amorphous content of both rods was effectively the same, i.e., they were both fully amorphous. In other words, the alloy ingot that produced in Experiment 3 was very close to the desired nominal composition, and thus the alloying procedure was considered successful. 

What is claimed:
 1. A method of making an alloy feedstock, comprising: forming a first composition by combining Fe element with a first nonmetal element; forming a second composition by combining Fe element with a plurality of transition metal elements; forming a third composition by combining the second composition with a second nonmetal element; and alloying the first composition with the third composition to form an alloy feedstock.
 2. The method of claim 1, wherein the first nonmetal element is B, P, Si, Ge, C, or combinations thereof.
 3. The method of claim 1, wherein the plurality of transition metal elements comprises Mo, Cr, Ni, Y, Co, Mn, Ga, Er, or combinations thereof.
 4. The method of claim 1, wherein at least one of the first nonmetal element and the second nonmetal element is a metalloid.
 5. The method of claim 1, wherein the second nonmetal element is Si, C, or both.
 6. The method of claim 1, wherein at the beginning of the forming the third composition the second nonmetal element is located under the second composition.
 7. The method of claim 1, wherein at least some of the elements have at least one dimension that is at least about 1 mm
 8. The method of claim 1, wherein the alloy feedstock is at least one of (i) homogeneous and (ii) not fully amorphous.
 9. The method of claim 1, wherein the alloy feedstock has a chemical formula of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂.
 10. The method of claim 1, wherein at least a portion of the making involves arc melting.
 11. A method of making an alloy feedstock, comprising: forming a first composition by combining Fe with a first nonmetal element; forming a carbon-containing composition by combining Fe with a plurality of transition metal elements and C; alloying the first composition with the carbon-containing composition to form an alloy feedstock.
 12. The method of claim 1, wherein the forming a carbon-containing composition further comprising forming a second composition comprising Mo, Cr, Y, Ni, or combinations thereof, before forming the carbon-containing composition.
 13. The method of claim 1, wherein the forming a carbon-containing composition further comprising forming a second composition by melting an alloy stack having a stack order of Mo disposed over Fe, which is disposed over Cr, which is disposed over Y.
 14. The method of claim 13, wherein the forming has a lower evaporation of at least one of Fe and Cr for the second composition relative to a composition not with the stack order.
 15. The method of claim 11, wherein the first composition comprises an intermetallic compound.
 16. The method of claim 11, wherein the alloy feedstock is substantially crystalline.
 17. The method of claim 11, wherein the alloy feedstock has at least one dimension of at least 2 inches.
 18. The method of claim 11, further comprising making the alloy feedstock into a bulk amorphous alloy.
 19. The method of claim 11, wherein at least some of the elements used in the making are not in powder form.
 20. The method of claim 11, wherein the first nonmetal element is B.
 21. A method of making an alloy feedstock, comprising: providing a Fe-containing first composition; combining C with a second composition comprising Mo, Cr, and Y to form a third composition; and combining the first composition with the third composition to form an alloy feedstock.
 22. The method of claim 21, wherein the first composition is iron boride.
 23. The method of claim 21, wherein the second composition has a stack order of Mo disposed over Fe, which is disposed over Cr, which is disposed over Y.
 24. The method of claim 21, wherein the alloy feedstock has a weight of at least 100 g and at least one dimension of at least 2 inches.
 25. An alloy comprising: a first composition comprising Fe and a first nonmetal element; a second composition comprising Fe, plurality of transition metal elements and a second nonmetal element; wherein the first composition is alloyed with the second composition in the alloy.
 26. The alloy of claim 25, wherein the first nonmetal element is B, P, Si, Ge, C, or combinations thereof.
 27. The alloy of claim 25, wherein the plurality of transition metal elements comprises Mo, Cr, Ni, Y, Co, Mn, Ga, Er, or combinations thereof.
 28. The alloy of claim 25, wherein at least one of the first nonmetal element and the second nonmetal element is a metalloid.
 29. The alloy of claim 25, wherein the second nonmetal element is Si, C, or both.
 30. The alloy of claim 25, wherein at the beginning of the forming the third composition the second nonmetal element is located under the second composition.
 31. The alloy of claim 25, wherein at least some of the elements have at least one dimension that is at least about 1 mm
 32. The alloy of claim 25, wherein the alloy is at least one of (i) homogeneous and (ii) not fully amorphous.
 33. The alloy of claim 25, wherein the alloy has a chemical formula of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂.
 34. The alloy of claim 25, wherein at least a portion of the making involves arc melting.
 35. The alloy of claim 25, wherein the second composition comprises a carbon-containing composition comprising C.
 36. The alloy of claim 25, wherein the second composition further comprises Mo, Cr, Y, Ni.
 37. The alloy of claim 36, wherein the second composition comprises a stack order of Mo disposed over Fe, which is disposed over Cr, which is disposed over Y.
 38. The alloy of claim 25, wherein the first composition comprises an intermetallic compound.
 39. The alloy of claim 25, wherein the alloy is substantially crystalline.
 40. The alloy of claim 25, wherein the alloy has at least one dimension of at least 2 inches.
 41. The alloy of claim 25, wherein the alloy comprises a bulk amorphous alloy. 